Prior to analytical testing of the cleanliness of surfaces, surfaces should first be visually assessed. This can be via direct observation, smell or the rubbing of the surface with a clean white cloth or gloves to try and determine any physical indications of soiling. Surfaces that are physically dirty, require no other testing to determine the success of the physical cleaning performance.
Measurement of any residues of food present on surfaces can then be carried out, typically with commercial ATP or protein test kits, and can give quick results during the cleaning process to establish whether a re-clean is required.
For example, ATP testing uses the presence of Adenosine Triphosphate on reaction to create pulses of light that can be read using an instrument. Also, protein or glucose testing and rapid allergen testing can identify any residues on a surface determining whether a re-clean needs to take place.
Specific tests exist called Lateral Flow Devices which can deliver a presence/absence result in a matter of minutes, ensuring that a surface can be made available for processing in the knowledge that the allergen of concern is not present.
The technology is similar to ELISA in that an antibody – antigen reaction is taking place with a visual indication revealing the presence or absence of the allergenic protein.
Using this technology either a food sample or environmental contact swab can be taken to test for the presence of, for instance: Peanut, Hazelnut, Almond, Casein (Milk), Egg, Gluten, Shellfish & Soya.
It is also possible to use DNA testing to look for allergens and animal species.
Any cleaning regime requires the selection of the correct detergent and disinfectant strength, with routine checks carried out to ensure that this desired strength has been met.
Most acid or caustic, cleaning in place (CIP), detergents can be monitored in-line by conductivity. The conductivity probe and controller must be calibrated, and temperature compensated, to ensure accuracy; as a rule, each 1°C rise in temperature will increase conductivity by approximately 2%.
With peracetic acid and chlorinated based products redox measurement is generally used because conductivity tends to be unreliable and inaccurate.
The strength of detergents or disinfectants should be checked regularly through chemical titration. This can be done either in a QC Laboratory using traditional burettes or by a dropper bottle method, with the chemistry identical in both. A common misconception is that a burette is more accurate than a dropper, but this is largely untrue.
Colour change test strips provide a quick indication on the approximate concentration of certain active components in a detergent or disinfectant; whilst pH paper will deliver a quick indication of any residual acidity or alkalinity following on from a detergent clean. Test strips looking for PAA and QAC can give a good indication as to the strength of the disinfectant.